Question

我正在尝试学习如何连接到API并接收和解析JSON数据，因此我目前正在关注此网页上的示例：http://www.whycouch.com/2012/12/how-to-create-android-client-for-reddit.html，但我收到的错误是：

E/fetchPosts(): org.json.JSONException: End of input at character 0 of

我的应用程序正在连接，因为它说已经建立了新的主机连接，因此我不太清楚为什么它会得到空白的响应。下面是我的类，它获取连接并读取内容。如果我不得不猜测我哪里出错了，我会说它与请求属性有关，但我去了reddit的网站并按照他们想要的格式化它并且它仍然没有返回任何内容。谢谢。

public class RemoteData {

/*
This method returns a connection to the specified URL,
with necessary properties like timeout and user-agent
set to your requirements.
 */

public static HttpURLConnection getConnection(String url){
    System.out.println("URL: " + url);
    HttpURLConnection hcon = null;
    try{
        hcon = (HttpURLConnection)new URL(url).openConnection();
        hcon.setReadTimeout(30000); //Timeout set at 30 seconds
        hcon.setRequestProperty("User-Agent", "android:com.example.reddittestappbydrew:v0.0.1");
    }catch(MalformedURLException e){
        Log.e("getConnection()", "Invalid URL: " +e.toString());
    }catch (IOException e){
        Log.e("getConnection()", "Could not connect: " + e.toString());
    }
    return hcon;
}

/*
A utility method that reads the contents of a url and returns them as a string
 */

public static String readContents(String url){
    HttpURLConnection hcon = getConnection(url);
    if(hcon == null) return null;
    try{
        StringBuffer sb = new StringBuffer(8192);
        String tmp = "";
        BufferedReader br = new BufferedReader(new InputStreamReader(hcon.getInputStream()));
        while((tmp = br.readLine()) != null){
            sb.append(tmp).append("\n");
        }
        br.close();
        return sb.toString();
    }catch(IOException e){
        Log.d("READ FAILED", e.toString());
        return null;
    }
}

}

Answer 1

您编写的代码对于从我的URL获取html / json响应数据看起来非常幼稚，因为没有在那里处理重定向。您可以通过检查hcon.getResponseCode（）来处理代码中的重定向，其值为200，以便您成功读取数据。如果它不是200和其他类似301（重定向）或403（需要授权）的东西，你需要相应地处理这些响应。

这里我给你一个简单的代码，它使用来自apache的HttpClient（我使用的是httpclient-4.2.1）库，并以String的形式获取响应。

import java.io.ByteArrayOutputStream;
import java.io.IOException;

import org.apache.commons.fileupload.util.Streams;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class HttpUtils {
    private static Logger LOGGER = LoggerFactory.getLogger(HttpUtils.class);

    public static String getResponse(String url) throws IOException {
        return getResponse(url, "UTF-8");
    }

    public static String getResponse(String url, String characterEncoding) throws IOException {
        return getByteArrayOutputStream(url).toString(characterEncoding);
    }

    public static byte[] getBytes(String url) throws IOException {
        return getByteArrayOutputStream(url).toByteArray();
    }

    public static ByteArrayOutputStream getByteArrayOutputStream(String url) throws IOException {
        HttpClient httpclient = new DefaultHttpClient();
        HttpGet httpGet = new HttpGet(url);

        HttpResponse response = httpclient.execute(httpGet);
        LOGGER.debug("Status Line: " + response.getStatusLine());
        HttpEntity resEntity = response.getEntity();

        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        Streams.copy(resEntity.getContent(), byteArrayOutputStream, true);
        return byteArrayOutputStream;
    }

    public static void main(String[] args) throws IOException {
        System.out.println(getResponse("https://www.reddit.com/r/AskReddit/.json"));
    }

}

使用此代码实现您的目标，如果您不想使用HTTPClient API，则修改现有代码以处理http状态代码，但使用上述代码很简单。

为什么我的Android应用程序连接到Reddit API，但获得空白响应？

1 个答案: